1. Field of the Invention
The invention relates to an electromagnetic wave propagating structure, more particularly to an electromagnetic wave propagating structure that surpasses diffraction limit and that enhances resolution and precision of optical systems which incorporate the electromagnetic wave propagating structure.
2. Description of the Related Art
Electromagnetic wave technology, especially optical technology, is one of the most widely used basic technologies in high-technological industries such as medical examination, precision measurement, semiconductor industry, etc. Therefore, the search for ways to enhance the resolution and precision of optical technology is what both the academic and industrial communities are striving for.
The behavior of light is limited by the diffraction limit, which restricts the minimum value of the product of angular divergence (sine of diffraction angle (sin θ)) and a width of light beam (2w). At present, the achievable highest resolution for a focused light spot in optical systems is approximately 0.61 times the wavelength of the incident light beam (half of the wavelength in 1-D). By surpassing the diffraction limit, light can be focused into a light spot having a size far below the wavelength of the light, thereby enhancing the resolution and precision of optical systems.
Currently, there exist three methods for enhancing optical resolution, which include reducing the wavelength of the light beam, increasing the refraction index of an optical medium through which the light beam propagates, and adopting an optical lens utilizing the half-angle of the maximum cone of light. Out of these three methods, the method involving reducing the wavelength of the light beam produces the most remarkable effects, and is thus the most widely used method. For example, in photoetching and lithography processes during semiconductor manufacturing, the wavelength of the light beam used for exposure and development is reduced to within the wavelength range of ultraviolet light. However, the problems with this method reside in the increasing difficulties encountered in further reducing the wavelength and the corresponding manufacturing techniques and the increasing costs required for building corresponding facilities, which eventually become a bottleneck for the advancement of related fields.
Therefore, how to surpass the diffraction limit that restricts various optical applications in order to enhance the resolution and precision of optical systems is a challenge to be dealt with.